Heat waves are becoming more pronounced and widespread in the United States. Clinicians need thus to be at the forefront of preventing heat-related illnesses (heat exhaustion, heat stroke) in patients taking antipsychotics for a serious mental illness like schizophrenia. This patient group is at increased risk for hyperthermia due to a confluence of illness factors, treatment, and their socio-economic situation.
Hyperthermia occurs when heat accumulation (internally generated and heat transfer from the environment) surpasses the body’s ability to dissipate heat. Four heat transfer modes (radiation, convection, conduction, and evaporation) play a role in temperature control. The skin via increase in sweating (evaporation) and blood flow to the surface (more radiation and conduction) is a major organ for heat regulation. However, if the ambient temperature is too high or too humid, the mechanisms for dissipating heat can no longer compensate and behavioral responses (reducing internally produced heat by resting, seeking cooler places) become critical.
Apart from general risk factors (older age, immobilization, acute illness), patients with schizophrenia because of disorganization, negative symptoms, or lack of judgment may not recognize the threat from exposure to heat; fail to take countermeasures (dressing appropriately, hydrating, staying in cool places); or even exercise in the heat. They may also not appreciate warning signs for heat exhaustion.
Antipsychotics affect heat regulations in two ways: One, central temperature regulation at the level of the hypothalamus is partially under dopaminergic control; blocking dopamine renders an organism more poikilothermic (more susceptible to the ambient temperature). Two, anticholinergic antipsychotics (or anticholinergics taken for extrapyramidal side effects) reduce the ability to produce sweat, reducing evaporative sweating. Other medications taken for medical reasons also impair heat regulation, particularly blood pressure medications including diuretics.
Finally, many patients with schizophrenia live in sub-optimal conditions; they may not have air conditioning for example or a social network that protects them.
Clinicians can help their patients avoid heat-related illnesses in several ways:
The basic principles of prevention are staying hydrated, staying cool, and staying safe. Below is a tip sheet that expands on these three principles.